Accretion definition, an increase by natural growth or by gradual external addition; growth in size or extent. See more.
Alveoli are tiny sacs within our lungs that allow oxygen and carbon dioxide to move between the lungs and bloodstream. Learn more about how they function and quiz your knowledge at the end.
There are about 300 million alveoli found in each lung of a human. The surface area resulted by alveoli for surface diffusion is about 80 m2, which is about 42 times the surface area of whole human body. The air space opening into two or more alveoli is called alveolar sac.